Nerve growth factor (NGF) is synthesized and secreted by two cell lines derived from the nervous system, the rat C6 glioma and the mouse NB2a neuroblastoma. The content of NGF is increased in either cell line by agents which elevate cyclic AMP: agonists of beta-adrenergic receptors for the glioma cells and prostaglandin E1 or adenosine for the neuroblastoma cells. Research is being carried out to determine: 1) whether the increase in NGF content caused by stimulation of specific receptors causing an increase of cAMP content is the result of new synthesis or of activation of a NGF precursor and 2) whether comparable changes of NGF content can be shown in sympathetic ganglia following administration of beta-receptors by injection or release of beta-adrenergic receptor agonists.